Guide for Treasure Hunter Achievement

Almost every quest you take on will contain secret rooms. These can be tricky to spot, but they do stand out. If you see a part of a wall that looks different from the rest of the surrounding walls, then hit it with A to reveal a hidden room with a big pile of gold and usually two chests (I encountered one room with several chests, must've been the only one since I opened pretty much every secret room there was). At the end of the quest/level, it'll tell you how many secret rooms you opened out of the total amount possible for that level. Should come naturally if you're going for the full 200G.